Striae distensae are very common lesions. They are present in most healthy adult women, having originated either during puberty or at the time of the first pregnancy. Stretching of the skin, as in rapid weight gain, or mechanical stress, as in weight lifting, often precedes their development. About 50 percent of pregnant women will develop these lesions, often referred to as stretch marks, on thighs, abdomen and breasts, starting at about 3 to 4 months of gestation. However, such lesions are also noted in cachectic states, for example in tuberculosis and typhoid fever, and they have also been noted after intense slimming diets.
The pathogenesis of striae distensae lesions is unclear. Some pregnant women do not develop the lesions; lesions have not been produced experimentally, and there is no animal model.
Clinicians are aware that striae distensae evolve over time passing through an early phase of inflammation (striae rubrae) and ending in the typical white stretch mark (striae albae). The striae rubrae are red, slightly elevated, linear lesions that may be tender. Later, the lesions flatten and the redness fades, leaving a permanent, wavy depression, which is the striae albae. The striae albae lesions may be 5 to 15 mm wide, depressed with a crinkly surface. These are the stretch marks which last for life, since to date there has been no known treatment.
The histopathology of striae, which always have the same appearance regardless of cause, has generated much dispute. However, P. Zheng et al., "Anatomy of Striae," British Journal of Dermatology, 112:185-193 (1985) present evidence that striae albae are true scars resulting from an earlier inflammatory process that destroys elastic fibers. They are not formed by stress-induced rupture of the dermal fibrous network.
Retinoic acid has been previously applied topically to the skin for the treatment of many skin disorders. See, for example the review of Thomas et al., "The Therapeutic Uses of Topical Vitamin A Acid," Journal of the American Academy of Dermatology, 4:505-513 (1981). It is known that tretinoin has an anti-inflammatory action useful in ameliorating chronic dermatoses such as psoriasis and lichen planus.
According to my U.S. Pat. No. 4,603,146, topical retinoic acid has been effective to stimulate formation of new collagen fibers, generate new blood vessels, correct abnormalities in elastic fibers, and eliminate neoplastic growths in chronically sundamaged skin. Retinoic acid is used world-wide to retard and reverse photodamage from excessive exposure to ultra-violet radiation in sunlight.
The literature also reports the improvement of post-acne, elevated, hypertrophic scars of the back with topical retinoic acid. These hypertrophic scars have a very different origin, following severe cystic lesions, resulting in a huge increase in collagen. In striae distensae the opposite happens; there is loss of collagen with atrophic scarring.